A natural history notebook and project of the Missouri Botanical Garden

Islands

James and Thibaud Aronson post here their second report on ecological restoration in New Zealand, an island nation that seeks to eradicate non-native predators by 2050.

The government of New Zealand (or Aotearoa, as the Maori call it) has announced its goal to be predator-free by 2050, but the effort and expense required to eradicate the tens of millions of noxious animal and plant pests from the entire country is mind-boggling. One important development is technological in nature. Invasive mammal-killing traps are not very costly, but they do require regular maintenance. Some companies, such as this one, are designing and manufacturing automatic traps that humanely kill pest animals and then reset themselves.

Much of the native fauna has only survived to this day because, in addition to the two main islands, New Zealand also possesses many small offshore islands, some of which were never reached by introduced pests, like rats and stouts. Eradication campaigns have for many years been carried out on various islands relatively near to shore, to make them ‘pest-free sanctuaries’, where small salvage populations of rare and endangered species have been translocated and established successfully. Several ‘mainland islands’ have also been established, on North Island and South Island, completely surrounded by massive pest-proof fences, with ongoing trapping and poisoning efforts to eliminate any predator that might manage to get in.

We visited Tawharanui, one such sanctuary in the north of the country. While it is in an area that still has some native forest, the contrast is remarkable as soon as one passes the fence. The first notable difference is an audible one. The birds of New Zealand are unusual in that they sing all day long, and they are loud. James Cook, the first European to set foot on the islands, described the birdsong as “deafening”. Today, most of the forests are quiet, and the few birds that can be heard are exotic species, introduced by nostalgic, home-sick Europeans. Tawharanui gives an idea of what things once were like. Within minutes, we were struck by the diversity and abundance of life, another world entirely compared with the unprotected and second growth forests. Half a dozen endemic species thrive here that can hardly be encountered anywhere else on the mainland, and all of them display the characteristic fearlessness that has caused their downfall.

A North Island robin (Petroica longipes), displaying the typical inquisitive behavior that has caused the extinction of so many insular birds worldwide.

A few days later, we took a boat to Tiritiri Matangi (“a place tossed by the wind” in Maori). This small island, an hour away from Auckland, is one of the country’s most famous wildlife sanctuaries, and a remarkable experiment in ecological restoration. It was intensively cultivated and pastured until 1971, when it passed back to government ownership, with the intention of making it a nature reserve. However, as natural regrowth was very slow, a massive volunteer program was launched in 1984, leading to the planting out of over 250,000 native trees in the next ten years. Under the guidance of Dr. John Craig, and colleagues, 25 years of work at Tiritiri Matangi has led to much restoration of both natural and social capital.

A key component was a large-scale pest eradication program applied with great thoroughness. Once the habitat was deemed suitable, several endangered species were translocated from other more isolated islands where they persisted, nearly all of which have since established successfully. The regenerating forest offers great opportunities to view the wildlife, and tens of thousands of people visit the island every year. The success of the project has since led to similar projects on other offshore islands in New Zealand.

The stitchbird (Notiomystis cincta), the sole representative of its family, was once common throughout New Zealand. Within a century of the Europeans’ arrival, only a few hundred birds persisted on a single offshore island. It has since been translocated to Tiritiri Matangi and several other pest-free islands.

New Zealand’s best tool in this struggle is probably its people. Great efforts have been made in communicating to children the uniqueness of their endangered species, and how essential is the eradication of the introduced pests, no matter how cute and cuddly they may be. This was true at Tiritiri Matangi, and everywhere else. See the two key references cited at the end.

A sign describing one of many community programs we saw, where locals carry out conservation work, such as this eradication program along the Kepler Track, near Te Anau, South Island.

Invasive exotic plants are also a serious obstacle to ecosystem recovery, especially various species of introduced conifers that have escaped commercial tree crop plantations and become naturalized and out-of-control on native grasslands little prepared for such an encroachment. But the use of native plants has really taken off, with sophisticated, and inspiring native plant nurseries found throughout the country, and everywhere from city gardens to public works projects, native plants being used more and more every year. As a result, native species, from green geckos to tuis, the country’s most famous songster, can now be seen right in the middle of Auckland.

A Tui (Prosthemadera novaeseelandiae) perched on a native Hebe shrub on Stewart Island.

Stewart Island, the country’s third largest island at 1750 km2, is an example of what the country as a whole could aspire to. Royal albatrosses come into the harbor following fishing boats, blue sun orchids bloom on the roadsides, and kiwis come out at night to forage on the rugby field.

Oban, the only settlement on Stewart island. Walk in any direction out of town, and you quickly find yourself entering the surrounding national park.

Now, of course, only 400 people live permanently on the island, 85% of which is a National Park, and most people on the island depend on tourism for income. The model obviously cannot be translated directly to the country as a whole. All dogs on the island must receive kiwi-avoidance training, and when a pair of variable oystercatchers decided to nest on the field in the middle of the primary school’s playground, the area was cordoned off, and several signs put up, telling children what a privilege it was that their school had been chosen by the parental pair, and to keep well away from the nest. The chick hatched while we were there, and happily crossed over the road safely, with his parents following the reckless chick, to the nearby beach. There too, even though people (but not dogs) are present every day and evening, except when it’s pouring down rain, these birds are nearly guaranteed a watchful and caring stewardship on the part of the locals and quickly tuned-in visitors. These simple things show a will on the part of the local people to exist within the native ecosystem, rather than imagining themselves outside it, and licensed to do whatever they will, and to hell with the consequences. The rest of the world would do well to take a page from NZ’s book.

James and Thibaud Aronson post here the first of two reports from New Zealand, where they spent the first three weeks of January 2017, learning about the remarkable restoration and conservation work going on there.

New Zealand, or Aotearoa (Land of the Long White Cloud, as the Maori call it), is one of the world’s leaders in terms of conservation and restoration. However, it certainly did not start off that way.

New Zealand was first settled by Polynesian sailors about 750 years ago, one of the last places on Earth to be colonized by humans. These pristine islands, which had stood in isolation for 80 million years, harbored a wealth of unique lifeforms, from the iconic kiwi (of which few people know there are in fact 5 species), to the weta (cricket relatives in one of several genera endemic to New Zealand, some of which are among the largest insects in the world), and the tuatara, large, endemic, lizard-like reptiles, the last survivors of an order that thrived 200 million years ago.

The island did not lack predators: just think of the now-extinct Haast’s eagle (Harpagornis moorei), the largest eagle to have ever lived, and the fierce, flightless moa (nine species in six genera; all extinct), giant relatives of the ostrich, the biggest of which stood fully 3.6 meters (12 feet) tall and weighed 230 kg (510 lb). However, Aotearoa harbored practically no land mammals, the only exceptions being two species of bats. Therefore, many native animals were flightless, absolutely unafraid of humans and their dogs, and thus very easy to hunt.

Faced with this incredible boon, the Maori did what humans have done on every single island and continent they have ever reached: they took and took without restraint. All 9 species of moa, the most rewarding of prey, were gone within 200 years. Seals, once abundant along all coastlines, vanished from many areas. Forced to change their ways, the Maori shifted to eating more fish and shellfish, and took to cultivation, burning down forests for cultivation, and also started eating the bracken fern that grew back in abundance after fires. However, and very unusually, having caused widespread extinctions, the Maori eventually introduced rāhui, a strict system of preventing all unauthorized persons to enter an area, or harvest a specific resource. The intention was to allow regeneration, such as certain animal food sources, or plant materials – such as wood from a certain tree species prized for carving, thus avoiding local depletion of resources or even further extinctions. This system is still in use today among Maori, and can also be declared by different agencies of the NZ government!

Billy Boy, a Maori guide in the Waipoua forest, whose connections to New Zealand’s wilderness is an essential part of his identity. Whenever one of his grandchildren was born, the first thing he did was to take them to the forest and begin their introduction to the natural world.

However, things took a significant turn for the worse 200 years ago, when Europeans reached New Zealand. They rapidly established large-scale logging activities, targeting the various species of native conifers, which can live for millennia and reach enormous sizes. For a few decades, whaling and sealing were vastly profitable as well, until populations crashed. What’s more, the Europeans brought with them cats, black rats, and later possums, stoats, and other carnivorous mammals. All of these species have since gone feral, and become one of the foremost ecological problems the country faces today. Since human settlement, 47 endemic bird species have gone extinct, about half from Maori over-hunting, and the remainder in the last 2 centuries, wiped out by feral predators, as were various species of reptiles, amphibians, and invertebrates. Many more species have no doubt suffered the same fate, disappearing before they were even documented.

However, in recent decades, New Zealand has made an impressive and inspiring commitment to preventing future degradation and in fact taken many great strides towards rolling-out restoration at a national scale. This merits celebration and emulation. During our 3-week trip, we got to see first-hand some examples of the conservation and restoration work underway.

One of the most iconic trees of New Zealand is the kauri (Agathis australis). These massive conifers once dominated the forests in much of the warmer, nearly subtropical, northern part of the country. They can live well past a thousand years, grow 50 meters tall, and reach a girth comparable to that of the Californian sequoias. The largest individual known today is called Tane Mahuta, or Lord of the Forest, the name of one of the main gods in Maori cosmology. It is hard to describe how insignificant one feels when standing below these giants.

Te Matua Nhgahere (Father of the Forest), the oldest and second-largest remaining kauri in New Zealand. The age of this tree is variously estimated to be between 1200 and more than 3000 years old. Such longevity is exceedingly rare in tropical or subtropical rainforest trees.

The kauri also happen to yield excellent timber, once particularly valued for ship-building. Their logging was only banned in 1972, and less than 4% of the original kauri forests are left today. Happily, no native forest can be legally logged anywhere in New Zealand today, thanks to an election promise of the Labour government which passed into law in 2002.

Waipoua forest, on the north-west coast of the North Island, is the largest kauri forest left in New Zealand. Great efforts are being made today to preserve the remaining stands, particularly focusing on halting the spread of kauri dieback disease, a horrific, recently-arrived fungus-born infection that spreads through soils and kills every kauri tree it infects. Part of the campaign to save the tree entails education and consciousness-raising among all visitors to the kauri forests as to the importance of cleaning their shoes and boots both when entering and leaving the area.

Skeleton of a kauri killed by the dieback disease in Waipoua forest. Can the disease be stopped?

Some forest areas have fared better, such as the Nothofagus forests of Fiordland National Park, in the south-west of the South Island, well protected as they are by billions of biting flies, which have successfully prevented any significant human settlement in the area. However, stoats, rats and possums are not so easily deterred, and the whole area is a prime example of empty forest syndrome.

Southern Beech forest (Nothofagus spp.) in Mt Aspiring National Park.

Therefore, enormous amounts of money are being spent on large-scale trapping and poisoning throughout the country, to try and control these non-native pests which wreak havoc both on native fauna and flora. For instance, we visited the private Pupu Rangi Sanctuary, 100 hectares of forest south of Waipoua, in the North Island. Its owner, Octavian Grigoriu, and a diverse team of volunteers work tirelessly in the forests, maintaining traps and poisoned bait around the whole perimeter of the forest, and deep in the bush as well. Octavian hosts paying guests, which helps pay for the expensive traps and poison. As a result, native species, including the North Island brown kiwi, are doing significantly better than in the nearby Waipoua forest, which is much larger, and therefore exponentially harder to protect effectively.

In sum, all over New Zealand, many initiatives, both top-down and bottom-up, are doing excellent work, which we will discuss in our second blog post.

Leighton Reid, a postdoctoral fellow in the Center for Conservation and Sustainable Development, reflects on tortoises, tree cacti, and ecological isolation.

The Galápagos is the world’s most pristine tropical archipelago, and it is utterly unique. Nearly the entire island group is a national park, and 200,000 visitors per year come to witness its ecological singularities ‒ things like penguins and iguanas swimming side-by-side through a mangrove lagoon. The archipelago consists of fourteen large, volcanic islands and over a hundred smaller rocks and islets. Most of the land surface is low and dry. The easternmost island is about 900 km from mainland Ecuador, which is a probable source for the organisms that first began to colonize Galápagos when its volcanic peaks surfaced above the Pacific five million years ago. Indeed, the islands’ ecology is characterized by their isolation. Each island contains a relatively low diversity of organisms, many of which are unafraid of large primates. The biotas’ ecological simplicity and naiveté have facilitated major scientific discoveries, such as that small, heritable variations can have life or death consequences for individuals and ultimately change populations.

One of the more bizarre life forms on Galápagos is the tree cactus. Prickly pear cacti (Opuntia species) are not particularly rare in the western hemisphere. In the United States, for instance, they occur in every state except Alaska. But over millions of years in Galápagos they have become quite varied. Some grow low to the ground, like the familiar continental forms, whereas others grow as trees, towering up to 15 m above the ground. The first botanist to speculate on this phenomenon was Alban Stewart (1911), a scientist-sailor with the California Academy of Science. He noted that erect, tree cacti tended to grow on islands that also housed another over-sized organism – the Galápagos tortoise (Chelonoidis nigra). Galápagos tortoises eat the fleshy cactus pads, which contain water – a limiting resource in arid environments. Stewart posited that the pressure from tortoises craning their long necks upward to munch cactus pads may have favored taller cacti.

Opuntia echios var. barringtonensis is one of the taller tree cacti, presumably made that way by pad depredation by giant tortoises over many generations.

A low-growing cactus (Opuntiaechios var. zacona) growing on Seymour Norte, an island that historically had no tortoises or iguanas. Herbivore pressure is visible here; an introduced land iguana (Conolophussubcristatus) has been taking bites from the lowest pads.

The relationship between tortoises and cacti was thrown into disarray after the Galápagos were discovered (accidentally) by Panamanian Bishop Tomás de Berlanga in 1535. By the late 19th Century, pirates and whalers removed thousands of tortoises from the islands, stowing the living animals in their holds as fresh meat for their long Pacific voyages. Eventually, overharvesting extirpated tortoises from several of the islands, with rippling effects on the rest of the ecosystem. Even where tortoises survived, they were often unable to reproduce because their offspring were eaten by introduced, European rats. Tree cacti were among the hardest hit; tortoise decimation stripped these plants of their main seed disperser.

Reintroduced giant tortoise in the littoral zone on Isabela Island.

In response to tortoise declines, the Charles Darwin Foundation and the Galápagos National Park Service began a captive breeding program on Santa Cruz Island. Since 1965 they have raised and repatriated thousands of tortoises to several islands, waiting to release them until the tortoises have gotten big enough to be “rat proof”. By and large the reintroductions have been successful. On Española Island, for example, tortoise populations had crashed to fifteen individuals in 1960, but by 2007 more than 1500 individuals had been repatriated, and the population appeared stable. Moreover, these reintroduced tortoises reinitiated seed dispersal for an endangered tree cactus (Opuntia megasperma var. megasperma), increasing the number of juvenile plants.

In addition to species reintroductions, ecological restoration in Galápagos has often entailed species eradications. Isolation historically shaped Galápagos ecology; nine hundred miles is a long way for a snake or a lizard to float on a vegetation raft. But Galápagos’s isolation was compromised by seafaring humans, who facilitated island colonization by domesticated animals and hundreds of plant species. Goats have been among the worst invaders. Until recently, goats overgrazed the islands’ vegetation, converting it into habitat unsuitable for native species. One of the most ambitious restoration projects in Galápagos has been eradicating goats from the archipelago. On the largest island, Isabela, more than 140,000 goats were killed in 2004-2005 using unconventional restoration tools, including helicopters, AR15 rifles, and Mata Hari goats – sterilized female goats induced into long-term estrus and fitted with radio telemetry collars to root out the last hold-outs. Goat eradication has resulted in spontaneous vegetation recovery. In addition to goats, the Charles Darwin Foundation and the Galápagos National Park Service have also eradicated eight exotic plant species. Other species will be harder to get rid of, like rats, guava, blackberry, and domestic cats.

Despite its one-of-a-kind nature, can the world’s most pristine tropical archipelago serve as a reference for other arid, tropical islands? That is, can we evaluate the success of other island restorations by comparing them to the relatively intact Galápagos’s ecosystem structure, function, and composition? Perhaps to some extent we can. Historical contingency leads to unique island assemblages (for example: giant tortoises in Galápagos, giant skinks in Cabo Verde, giant lizards in Komodo), but many islands may be characterized by their lack of functional redundancy. In other words, if you remove a species from an island, the ecosystem consequences may be greater than if you had removed a species from a more diverse mainland ecosystem. Additionally, plant restoration in the arid Galápagos suggests that when disturbances are removed, vegetation can recover rapidly. This may also be true of other oceanic archipelagos, whose plants and animals have already colonized difficult terrain from a long way away.